A silver halide light-sensitive color photographic material is regarded as a matured product with the extremely high degree of accomplishment. On the other hand, required improvements in the performance are branched to various qualities such as high sensitivity, high image quality, minimum variation in performance independent of storage conditions and the like. Furthermore, for the future, rapid access processing properties such as an increase in development speed are further required. In recent years, the required level has been increasingly elevated.
Particularly, regarding the increase in sensitivity, on account of technical progress of a digital camera, in order to keep the superiority of a silver halide light-sensitive color photographic material, a further increase in sensitivity is required, while maintaining low fog and excellent storage stability.
As the sensitivity increase technique of a silver halide emulsion, that is, sensitization technique, various methods are known, which are those regarding production of a silver halide emulsion; chemical sensitization thereof, spectral sensitization thereof; a design method of a silver halide light-sensitive material; development process thereof, and the like. Of them, the spectral sensitization technique which increases the sensitive region of a silver halide is indispensable in terms of efficient recording of information.
The spectral sensitization is performed by allowing a cyanine dye or merocyanine dye to be adsorbed to a silver halide crystal and by transferring light energy absorbed by the dye to the silver halide crystal as an energy acceptor.
Furthermore, it is known that in the visual sensation of human beings, the highest sensitivity is exhibited for green light. Therefore, it is particularly required that the a color photographic material has sufficient green sensitivity and appropriate spectral sensitivity.
In the silver halide light-sensitive color photographic material of the present invention, in order to realize excellent color reproduction, the green-sensitive layer is spectrally sensitized in the region of 500 to 600 nm and the spectral sensitivity maximum are preferably in the wavelength region of 530 to 540 nm.
Conventionally, many patents have disclosed the spectral sensitization in the green region. The spectral sensitization techniques are disclosed in which each of dyes described below is individually employed; oxacarbocyanine dyed described in U.S. Pat. Nos. 2,647,053, 2,521,705, and 2,072,908, and U.K. Patent No. 1,012,825, etc.; benzimidazolocarbocyanine dyes described in Japanese Patent Publication Nos. 38-7828, 43-14497, or U.K. Patent No. 815,172, and U.S. Pat. Nos. 2,778,823, 2,739,149, 2,912,329, 3,656,959, etc., and oxathiacarbocyanine dyes described in U.K. Patent No. 1,012,825.
Furthermore, supersensitization techniques obtained by the combination of oxacarbocyanine dyes with the other dyes are disclosed in Japanese Patent Publication Nos. 43-4936, 43-22884, 44-32753, 46-11627, and 48-25652, and Japanese Patent Publication Open to Public Inspection Nos. 46-38694, 57-14834, etc.
When the above-mentioned dyes are employed, green sensitivity is enhanced. However, because the spectral sensitization region is shifted to a longer wavelength, it becomes difficult to obtain excellent color reproduction.
As sensitizing dyes which spectrally sensitize a region having a wavelength shorter than 550 nm, those are known, for example, carbocyanine dyes described in Japanese Patent Publication No. 44-14030, Japanese Patent Publication Open to Public Inspection No. 51-31228, and U.S. Pat. No. 2,441,342; cyanine dyes described in U.S. Pat. Nos. 2,072,908 and 2,231,658, Germany Patent No. 973,291; dimethinemerocyanine dyes described in U.S. Pat. Nos. 2,493,748, 2,519,001, and 3,480,439. However, when any of these dyes is employed individually, a photographic emulsion having the high green sensitivity is not obtained. When the increase in sensitivity is intended, problems have been caused in that fog is liable to be caused and storage stability is liable to be degraded.
Furthermore, even though a conventional spectral sensitizing dye for the short wavelength known in the art such as disclosed in Japanese Patent Publication Nos. 50-40662, 48-41205, 46-7782, 51-107127, 51-115620, 52-18311, 52-37422, 63-197936, and 63-239436, is employed in combination, the shorter wavelength region of green light cannot be efficiently spectral-sensitized and the storage stability under the condition of high temperature and high humidity has not been satisfactory.
As dyes having a spectral sensitivity maximum in the shorter wavelength region of green light, benzimidazoloxacarbocyanines and polycyclic condensed thiacyanine are known. However, due to the unsymmetrical arrangement of heterocyclic groups and a structure having a short methine chain, the above-mentioned dyes have a low molecular extinction coefficient and even though spectral sensitivity spectrum is formed which has a spectral sensitivity maximum in the range of 530 to 540 nm, high sensitivity has not been sufficiently obtained.
In recent years, a technique is disclosed in which the maximum sensitization wavelength of benzimidazolocarbocyanine dyes with a large molecular extinction coefficient known as performing efficient spectral sensitization of the longer wavelength region of green light is shifted to the shorter wavelength.
For example, Japanese Patent Publication Open to Public Inspection Nos. 5-88293 and 6-509657 disclose a benzimidazolocarbocyanine dye forming the J-band in a relatively short wavelength near 550 nm in which a trifluoromethyl group is substituted onto a ring and a methyl group is substituted for a nitrogen atom, and Japanese Patent Publication Open to Public Inspection No. 9-59527 discloses a benzimidazolocarbocyanine dye which is substituted with an N-o-sulfobenzyl group, forming a J-band in a relatively short wavelengths near 540 to 560 nm.
When these dyes are employed singly or in combination, the sensitivity maximum is still in a longer wavelength region and a shift to the shorter wavelength region has been required.
Furthermore, Japanese Patent Publication Open to Public Inspection Nos. 6-118540 and 6-118588, and Japanese Patent Application Nos. 8-022446 and 8-129770 describe benzimidazolocarbocyanine dyes which combine with a benzimidazole ring via a sulfonyl group. However, the shift of a spectral sensitivity maximum to a shorter wavelength region of green light is not sufficient and all the properties such as sensitivity, fog, storage stability under the condition of high temperature and high humidity, etc. are not sufficient. Thus further improvements have been required.